Secreted progranulin is a homodimer and is not a component of high density lipoproteins (HDL)

J Biol Chem. 2013 Mar 22;288(12):8627-35. doi: 10.1074/jbc.M112.441949. Epub 2013 Jan 30.

Abstract

Progranulin is a secreted glycoprotein, and the GRN gene is mutated in some cases of frontotemporal dementia. Progranulin has also been implicated in cell growth, wound healing, inflammation, and cancer. We investigated the molecular nature of secreted progranulin and provide evidence that progranulin exists as a homodimer. Although recombinant progranulin has a molecular mass of ∼85 kDa by SDS-PAGE, it elutes in fractions corresponding to ∼170-180 kDa by gel-filtration chromatography. Additionally, recombinant progranulin can be intermolecularly cross-linked, yielding a complex corresponding to a dimer (∼180 kDa), and progranulins containing different epitope tags physically interact. In plasma, progranulin similarly forms complexes of ∼180-190 kDa. Although progranulin partially co-fractionated with high density lipoproteins (HDL) by gel-filtration chromatography, we found no evidence that progranulin in mouse or human plasma is a component of HDL either by ultracentrifugation or by lipid binding assays. We conclude that circulating progranulin exists as a dimer and is not likely a component of HDL.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apolipoprotein A-I / metabolism
  • HEK293 Cells
  • Humans
  • Intercellular Signaling Peptides and Proteins / blood
  • Intercellular Signaling Peptides and Proteins / isolation & purification
  • Intercellular Signaling Peptides and Proteins / metabolism*
  • Lipoproteins, HDL / blood*
  • Lipoproteins, HDL / isolation & purification
  • Mice
  • Mice, Knockout
  • Progranulins
  • Protein Interaction Domains and Motifs
  • Protein Structure, Quaternary
  • Recombinant Proteins / blood
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism

Substances

  • Apolipoprotein A-I
  • GRN protein, human
  • Intercellular Signaling Peptides and Proteins
  • Lipoproteins, HDL
  • Progranulins
  • Recombinant Proteins